January 31, 2013

Star-Nosed Mole Reveals Mysteries Of Touch And Pain Sensing Molecules

Located just about an inch above the human elbow is one of the most sensitive patches of skin on our body. An excess of nerve endings in this region means just a light pinch will have even those with the highest pain thresholds flinching and begging for mercy. But humans are not even in the running when it comes to hyper-sensitivity on the skin.

Another mammal, the star-nosed mole (named for the star-shaped tip of its snout), has been found to have a higher proportion of touch-sensitive nerve endings than pain receptors. A study on this discovery, published this week in the journal PLoS ONE, was authored by Diana Bautista and colleagues from the University of California, Berkeley and Vanderbilt University.

While very little is known about how the sensations of touch and pain are detected in our cells, the fact remains, these sensations are very closely intertwined.

The research team, in an effort to broaden our understanding, set their sights on a very unique animal: the star-nosed mole (Condylura cristata). This specific mole is a small, semi-aquatic mammal whose home is typically found in the low wetlands of eastern North America. It is a burrowing animal, known to reside in a network of narrow underground tunnels. Due to the fact this animal exists in an environment of almost complete darkness, the star-nosed mole has poorly-developed eyes which renders it virtually blind.

This is where the star-nosed mole´s very interesting nose comes into play. The 11 pairs of finger-like appendages around the snout of the star-nosed mole help the animal in discerning, with some rapidity, if what it has come across is edible or not. This rapidity is so unique that the star-nosed mole recently won a spot in the Guinness World Records as the world´s fastest forager.

The small mole achieved this impressive distinction due to the fact that it is able to touch 13 separate areas of the ground every second. The recognition as fastest forager was achieved as a result of the mole´s ability to consume 8 separate prey items in less than 2 seconds. This stunning consumptive feat is possible, in no small part, thanks to the snout and accompanying appendages being one of the most sensitive tactile organs known in the animal kingdom.

Possessing the highest density of nerve endings known in any mammalian skin, with over 100,000 fibers in an area less than a half inch in diameter, researchers were able to determine that these nerve endings were specifically geared to detect light touch. In fact, this skin possessed a much lower proportion of neurons that are meant to detect, and respond to, pain.

The research team noted that the touch and pain receptors they identified in the star-nosed mole have also been detected in sensory receptors in both mice and humans. This suggests, according to researchers, that these receptors are likely to be more common across other mammals as well.

They believe their results highlight the importance of researching and examining the more diverse and highly specialized species around us. As a result, the fundamental aspects of biology, common across different animals, could be revealed.

According to lead author Bautista, “By studying the star-nosed mole, we identified candidate genes that may mediate touch and pain. These genes represent new potential targets for the development of much needed drugs and therapies to treat chronic pain.”